The present invention relates to a multi-piece solid golf ball of three or more layers which is composed of a solid core, an intermediate layer and a cover, and is endowed with excellent properties such as flight performance, feel on impact and controllability.
In recent years, the number of layers in solid golf balls has been increased from the conventional two-piece ball construction composed of a solid core and a cover by additionally providing an intermediate layer between the solid core and the cover, and efforts are being made to optimize each of the layers. Various three-piece golf balls have been disclosed in which a good flight performance and an excellent durability, feel and controllability are achieved by giving the core itself an optimized hardness profile and by providing the ball as a whole—including the core, the intermediate layer and the cover—with an optimized hardness profile.
For example, JP No. 3505922 (and the corresponding specification of U.S. Pat. No. 5,830,085) discloses a three-piece solid golf ball having a core, an intermediate layer and a cover, which ball satisfies the following relationship: core center hardness<core surface hardness<intermediate layer hardness<cover hardness. However, this golf ball has a low rebound.
JP No. 3772252 (and the corresponding specification of U.S. Pat. No. 6,565,455) discloses the use of the specific resin mixture mentioned in paragraph [0007] as the intermediate layer and/or cover material. Although using such an intermediate layer and/or cover material does enable a high rebound to be achieved in the golf ball, improving the durability remains a problem.
U.S. Pat. Nos. 6,409,614, 6,277,035 and 7,160,211 disclose multi-piece solid golf balls having a core, a soft inner cover and a hard outer cover, which outer cover is an ionomer cover having a high Shore D hardness. However, because the cover is too hard, these golf balls have a low spin performance on approach shots.
In the golf ball of U.S. Pat. No. 6,561,928, the total thickness of the cover encasing the core is too large, resulting in a decrease in flight performance. Other prior art includes the multi-piece solid golf ball disclosed in JP-A 2004-49913 (and the corresponding specification of U.S. Pat. No. 6,663,507).
U.S. Pat. No. 6,991,562 discloses a multi-piece solid golf ball having an inner cover layer formed of an ordinary ionomeric resin and an outer cover layer formed of a urethane resin. However, because this ball has a low rebound, achieving both a good flight performance and a good spin performance on approach shots is difficult.
Because the many multi-piece solid golf balls which have been disclosed to date fail to satisfy all the desired attributes—namely, flight performance, feel on impact, controllability/spin performance and durability, a need has been felt for further improvement.